The invention relates to an apparatus for the deposition of melamine from hot reaction gases.
U.S. Pat. No. 3,388,533 discloses that the melamine obtained in a catalytic melamine synthesis can be deposited from hot reaction gases, for example by cooling, on cooled metal walls or in a fluidized bed of melamine crystals. The crude melamine obtained is very contaminated and must be purified by expensive recrystallization. According to the invention described in U.S. Pat. No. 3,388,533, pure melamine can be obtained without additional recrystallization by separating the hot, melamine-containing reaction gases directly in a wash liquid after the synthesis in order to avoid decomposition reactions and contamination. In this process, pure melamine is obtained in a very simple manner, but the process has the disadvantage that very high reaction gas temperatures of about 440.degree. C. are required at the entry point of the reaction gases into the deposition apparatus in order to prevent deposits of melamine or blockage of the apparatus with solid melamine. It was the object of the invention to provide an apparatus which permits melamine deposition even at lower reaction gas temperatures. It was found, unexpectedly, that this object can be achieved by a combination of different construction measures in which, on the one hand, heatable apparatus parts and, on the other hand, apparatus parts which inhibit back-flow of the reaction gases from the absorption container are used.